Don McGahn, left, a top Washington election lawyer, was caught in the spotlight when Donald Trump pulled him up on stage for his New Hampshire primary night party on Feb. 9. (David Goldman/Associated Press)

The night Donald Trump notched his first win as a presidential candidate, he took the stage in New Hampshire between Ivanka and Melania and lit into the special interests that he declared had corrupted Washington — the company town that Trump, marketer extraordinaire, has ruthlessly trashed to the benefit of his own brand.

“These are lobbyists, these are people that don’t necessarily love our country,” said Trump. “We have to stop it. We have to stop it.”

Over Trump’s shoulder, another ruddy-faced man licked his teeth and flattened his lips into a straight line. He appeared out of place on that stage, and he seemed to know it. His face oscillated between forced smiles and blank stares, like Dustin Hoffman at the end of “The Graduate.”

This would be Donald F. McGahn II, the former chairman of the Federal Election Commission, Trump’s campaign lawyer and unofficial liaison to the Washington establishment his client was gleefully trashing.

It’s possible to read too much into the expressions of the men who stand behind Trump. (Did Chris Christie really feel like a hostage, or is that just what his face always looks like?) And yet one had to wonder what McGahn, who had skillfully outmaneuvered those who had tried to get Trump thrown off the New Hampshire ballot, really felt about his presence in the campaign’s antiestablishment tableau.

McGahn is one of the top election lawyers in the country, a job so highly specialized that its practitioners are almost unavoidably “Washington insiders” by definition. He is credited as one of the people most responsible for loosening regulations on campaign spending, an enabler of the corporate electioneering against which Trump has defined his candidacy. His wife, Shannon McGahn, is staff director for the House Financial Services Committee, a role that makes her a magnet for the very lobbyists that Trump regularly pillories.

As a possible convention fight looms, Trump has attempted to professionalize his campaign, hiring veteran lobbyist Paul Manafort, who wrangled Gerald Ford’s delegates in 1976. But it’s been years since Manafort lived full time in the District, and he remains a mystery to the K Street set. That makes McGahn the most entrenched Beltway insider in a campaign run by outsiders who owe their careers to Trump — which means McGahn may have the most to lose by appearing in frame with the candidate as he lobs bombs on the nation’s capital.

The chatter among his fellow Republican operatives hit a fever pitch when McGahn made his onstage debut with Trump. “It’s one thing to represent him as a lawyer,” said one, “but why would he lend his visual credibility to Trump in such a way that could damage his reputation for the long term?”

Then again, if any member of the “establishment” would be willing to gamble on a Donald Trump presidency, there are plenty of reasons why it would be Don McGahn.

In the 1980s, a young Donald Trump had his sights set on a different kingdom to conquer.

Atlantic City had recently passed legislation to allow casinos, and Trump wanted a piece of the action. Doing so required a power broker, someone who understood the intricacies of both the law and local political forces. So Trump turned to a portly Irish American lawyer named Patrick McGahn — “Paddy” to his friends, and Uncle Pat to his nephew Don.

Paddy, the son of a shopkeeper and recipient of three Purple Hearts from the Korean War, was known to have the best professional connections in town, and the high legal fees worthy of them. As Trump gobbled up real estate, Paddy paved the way.

When Trump was seeking city approval to build an employee parking lot at Trump Castle, Paddy threw a party for the mayor’s wife, inviting about 16 people aboard the Trump Princess yacht and taking them out to a dinner at one of the casino’s gourmet restaurants, according to news reports at the time.

There was no problem too big or too small for Paddy, who once represented Trump in a fight with a vendor selling hot dogs outside a Trump property. Trump was so appreciative that he named a cocktail lounge for him at the Taj Mahal in Atlantic City: Paddy’s Saloon.

The dealmaker didn’t even mind paying top price, according to John R. O’Donnell, former president of the Trump Plaza Hotel and Casino. In his book, “Trumped!,” O’Donnell recounted the time he complained to his boss about McGahn’s exorbitant fees.

“Jack, I’m 13 and 0 with this guy,” Trump said. “What do you want me to do? He gets things done in this town.”

Did Trump recognize a name he could trust when he decided to hire Don McGahn to get things done in This Town? McGahn did not respond to repeated requests for an interview, nor did the Trump campaign.

“I got to believe that Trump came to Don because of Pat, that’s got to be the connection,” said Bill Pascrell III, a lobbyist who worked on behalf of Trump casinos for more than a decade. “When Trump needed an election lawyer, I doubt he just Googled ‘good election lawyers.’ ”

McGahn during his tenure as on the Federal Election Commission in April 2013, when he was known for loosening many campaign finance regulations. (Bill O'Leary/The Washington Post)

Even if he had, he could easily have landed on McGahn. There aren’t many top-tier election lawyers, and even fewer with a résumé as strong as McGahn’s.

At the FEC, he frustrated campaign finance reform advocates by pushing to minimize government oversight; the commission’s top lawyer resigned when McGahn attempted to keep his office from sharing information with federal prosecutors. But he also won praise for opening up many formerly closed-door deliberations. He later moved on to the campaign-finance practice at the law firm Patton Boggs LLP and spent nearly 10 years as counsel for the National Republican Congressional Committee. Currently, he hangs his hat at Jones Day, another high-profile law firm.

Despite McGahn’s establishment bona fides, he makes a surprisingly good fit with the insurgent candidate.

“I could see them getting along,” said Jack Deschauer, who worked with McGahn at Patton Boggs. “Don’s a straight shooter, tells it like it is, and isn’t at all stuck up.”

He’s always been a bit of an iconoclast. Until recently he kept his hair long, and he still plays bass in an ’80s cover band that gigs in Ocean City, Md. While many of his colleagues boast Ivy League diplomas, McGahn got his law degree from Pennsylvania’s Widener University. Like Trump, he’s something of an outsider no matter how far inside he gets.

But there’s another reason McGahn may have been willing to work for Trump.

Shortly after McGahn started at Jones Day he picked up a new client: Aaron Schock, the congressman who was reeling from a scandal involving the misuse of federal funds and has since left office. To this day, according to FEC reports, Schock has still not paid Jones Day the nearly $750,000 he owes them. (Jones Day representatives also did not return calls.)

Getting stiffed by Schock put McGahn in a difficult position with his new law partners, said a Republican strategist who has worked with him. “He had this huge hole to fill. And when Trump came along, he was under a lot of pressure by management to fill that hole.”

So far, according to FEC reports, Trump has filled nearly $700,000 of that hole.

McGahn mostly has stayed behind the scenes since the New Hampshire rally, but his name has continued to pop up. He organized a meeting between Trump and members of Congress and accompanied the candidate to a recent meeting with the Republican National Committee. He’ll be there to help navigate the labyrinthine delegate and convention rules as the nomination fight enters the home stretch. And if Trump ever does decide to lean on outside money, he couldn’t have picked a better lawyer to have in his corner.

“It’s crucial to know all the rules and the laws, so you don’t get screwed,” said Barry Bennett, a senior strategist for Trump who touches base with McGahn several times a week. “No one knows the rules better than Don McGahn, since he wrote most of them.”

For a while, McGahn’s colleagues at Jones Day either didn’t know the firm was representing Trump or didn’t mind. That changed late last month when McGahn organized a meeting between the candidate and more than a dozen lawmakers at the firm’s Washington office.

Many current employees just about lost their minds, according to David Lat, a former federal prosecutor who runs the blog Above the Law and closely monitors the chatter within the nation’s white-shoe legal shops. Last month Lat quoted a number of his Jones Day sources, anonymously, saying that they were deeply embarrassed by the Trump affiliation.

But wait a minute. There are lawyers out there representing perverts, hucksters and neo-Nazis. Is working for Trump really that much worse?

In a sense, says Lat, it could be.

“To represent someone in a campaign is almost like being a consigliere to a crime family: You are in-house and working to advance the mission,” explained Lat. “It’s not like representing someone in court against some kind of attack. It’s essentially like being an aide to the message.”

And Trump’s message is a tough one for folks at Jones Day to swallow. The firm favors Republican clients, but its sensibility is moderate. It has many clients in Latin America, where Trump’s inflammatory talk on immigration does not play well. Megyn Kelly, the lawyer-turned-Fox News host whom Trump has repeatedly attacked, is one of the firm’s notable alumni.

Then there’s Benjamin Ginsberg, the preeminent election lawyer in the country and McGahn’s mentor and Jones Day co-worker. Ginsberg, who made his name in 2000 arguing the Republican side in Bush v. Gore, started the election cycle working for Wisconsin Gov. Scott Walker. He now spends much of his time on MSNBC helping explain delegate counts and convention scenarios to a bewildered electorate.

So, Mr. Ginsberg — Is it ethical to go on television and discuss the 2016 election while the GOP front-runner shovels money into your firm’s coffers? When you outline the convention strategies other candidates might take to wrestle the nomination from Trump, do you not worry about offending your own firm’s billionaire client?

Nope, says Ginsberg: That’s just not how big law firms work.

“We work together, but we also have walls,” he said, and Jones Day has built “a big, beautiful wall” for the presidential election.

It’s hard to say whether this explanation will satisfy anyone. These days, many members of the Republican establishment say there’s a special place for Republicans who work for Trump.

“I think that anybody that is enabling or contemplating Donald Trump represents a betrayal of Republican principles,” said Juleanna Glover, who has worked for Jeb Bush and Jon Huntsman. Even fellow election lawyers admit that picking up a client constitutes some kind of endorsement: “I would never work for a candidate I don’t believe would make a good president,” said Trevor Potter, who served as Sen. John McCain’s campaign counsel.

But don’t bet on McGahn getting blacklisted anytime soon, by the establishment or anyone else. Memories are short, and election lawyers are forever. Or, as Ryan Williams, a former Mitt Romney staffer put it: “They’re like accountants or undertakers. There’s always a demand for their profession.”

Ben Terris is a writer in The Washington Post's Style section with a focus on national politics. He previously worked at National Journal, where he wrote political features primarily focused on Congress.